User-defined Functions (UDFs) in SQLY

📖 Introduction

SQLY supports user-defined functions (UDFs) to extend its capabilities by creating reusable logic for queries.

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🔧 Defining a User-defined Function

Users can create custom functions with parameters and return types.

✅ Example 1: Define a Simple Function

udf:
  name: calculate_tax
  parameters:
    - name: price
      type: float
    - name: tax_rate
      type: float
  return_type: float
  body: |
    return price * tax_rate

This defines a calculate_tax function to compute tax based on a given price and tax rate.

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📌 Using UDFs in Queries

UDFs can be called in SQLY queries to process data dynamically.

✅ Example 2: Apply a UDF in a Query

query:
  select: [product_id, calculate_tax(price, 0.07)]
  from: products

This applies the calculate_tax function to compute tax for each product dynamically.

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🏗️ Advanced UDF Features

SQLY supports advanced UDF capabilities, including conditional logic and iteration.

✅ Example 3: UDF with Conditional Logic

udf:
  name: discount_price
  parameters:
    - name: price
      type: float
  return_type: float
  body: |
    if price > 100:
      return price * 0.9
    else:
      return price

This function applies a discount for prices above 100.

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🚀 Registering External Functions

SQLY allows integration with external libraries or APIs within UDFs.

✅ Example 4: Call an External API in a UDF

udf:
  name: get_exchange_rate
  parameters:
    - name: currency
      type: string
  return_type: float
  external:
    type: REST
    endpoint: "https://api.exchangerate.com/latest"
    method: GET
    query_params:
      base: "USD"
      target: "currency"

This function fetches exchange rates from an external API.

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📌 Summary

• Define UDFs with parameters and return types.
• Use UDFs dynamically in queries.
• Implement conditional logic within functions.
• Register external functions to call APIs or libraries.